1. Field of the Invention
The present invention relates to a system for preventing unauthorized operation of a motor vehicle, and, more particularly, to such a system specifically applicable to preventing operation of an automotive vehicle having its engine under control of a microprocessor.
2. Description of Related Art
It is well known that a large number of automotive vehicles are stolen each year or are taken by unauthorized persons for "joy riding" purposes. Many devices and apparatus have been proposed for preventing such unauthorized use of a vehicle, however, they all have been found not to be fully satisfactory in that they are relatively expensive, complicated to use, not sufficiently reliable, or they are readily circumvented by the would-be thief or joy rider.
Many of the present day automotive vehicles are so constructed as to have many of the engine functions (e.g., ignition, fuel ignition) under the control of a micro processor. Co-pending U.S. patent application No. 07/553,715, A SYSTEM FOR PROVIDING SECURE ACCESS TO A PROTECTED UNIT, by E. C. Posner and P. K. Sotel, discloses apparatus for securing access to various protected units including an automotive vehicle controlled by a microprocessor. Briefly, the patented system has an optical scanner which reads a prescribed unique optical code on a key device (e.g., ignition key) and on the code being found to coincide with a stored code produces a set of actuation signals. The actuation signals energize a crossbar switch unique for each vehicle which then interconnects a plurality of different functional elements in the vehicle necessary for vehicle operation. Specifically, the crossbar switch when properly energized interconnects the computer with those portions of the motor apparatus which are being controlled by the computer. When attempt is made to operate the vehicle without the correct key device, the signals coming to and from the processor do not make their way to the correct end location because of the scrambled circuit arrangement through the crossbar switch and in this way operation of the vehicle is prevented. The code on the key device is carried by an optical microchip with the reading thereof accomplished by a laser scanning system.